A medical diagnostic X-ray apparatus of the type mentioned in the opening paragraph is known from German Utility Model DE 295 10 802 U1. The known X-ray apparatus is an X-ray apparatus which is suitable for surgical applications. This X-ray apparatus is provided with a C-arm as a hollow carrier to which the X-ray source is connected, and has a cooling device comprising a double-walled envelope of the X-ray source. A cooling agent flows through the double-walled envelope of the X-ray source, said cooling agent being supplied through cooling agent conduits and being discharged by a cooling unit located outside the C-arm. The cooling unit, the cooling agent, the cooling agent conduits and the double-walled envelope of the X-ray source form part of the cooling device of the known X-ray apparatus.
During operation of an X-ray apparatus, the production of X-rays by the X-ray source causes the generation of much heat. If this heat is not dissipated, the temperature of the X-ray source increases and eventually also the temperature of the rest of the X-ray apparatus increases. If the temperature of the X-ray source exceeds a certain threshold value, the X-ray apparatus is automatically switched off for safety reasons and the temperature of the X-ray source first has to decrease to a value below said threshold value before the X-ray apparatus can be switched on again. In order to ensure that, in comparison with X-ray apparatus without a cooling device, a longer, uninterrupted time of operation of an X-ray apparatus is possible, the known X-ray apparatus is provided with a cooling device.
For surgical applications very strict rules apply as regards the hygiene in treatment rooms, so that patients with open wounds cannot be infected by pathogens and the like. The use of X-ray apparatus with a cooling device causing air or another cooling agent to be blown into the treatment room is therefore not allowed. In the known X-ray apparatus, which is suitable for surgical applications, the X-ray source is cooled by means of a cooling device having a double-walled envelope of the X-ray source through which a cooling agent flows. A cooling unit located outside the C-arm ensures that the cooling agent is first passed through a first cooling agent conduit, which extends partly via the inside of the C-arm, and then supplied to the double-walled envelope of the X-ray source. There the cooling agent absorbs part of the heat generated by the X-ray source during the production of X-rays and, subsequently, the cooling agent is carried away again to the cooling unit through a second cooling agent conduit which extends partly through the C-arm.
In order to be able to correctly position the X-ray source with respect to a patient, without the position of the X-ray source varying during operation of the X-ray apparatus, the C-arm is accurately balanced. A mass-change of the C-arm can disturb this delicate balance. In order to keep the disturbance of the balance of the C-arm to a minimum, as compared to an X-ray apparatus without a cooling device, the mass-increase of the C-arm is kept as small as possible in the case of the known X-ray apparatus. To achieve this, the cooling unit is placed outside the C-arm and, as compared to an X-ray apparatus without a cooling device, an increase of the mass of the C-arm is caused only by the double-walled envelope of the X-ray source, the cooling agent conduits, insofar as they are situated in the C-arm, and the cooling agent present in the cooling agent conduits in the C-arm.